Superconducting Quantum Interference Devices (SQUIDs) can comprise tiny loops of superconducting material in which one or more Josephson junctions interrupt the loop path. A Josephson junction can be a region of material that can provide a weak link between two fully superconducting regions. Superconducting electrons can quantum mechanically tunnel across the Josephson junction in a well-understood process.
The DC SQUID can have two symmetrical Josephson junctions, and DC SQUIDs can typically sense extremely small magnetic fields. Non-uniforms arrays of DC SQUIDs and DC bi-SQUIDs, which are DC SQUIDs with an additional Josephson junction bisecting the superconducting loop, have been modeled in different array designs and coupling schemes in the prior art, to determine their linearity and sensing capacities. SQUIDs have been fabricated in both low and high temperature superconducting materials. SQUIDs can be extremely sensitive; a SQUID-based sensor can detect minute magnetic fields and can be decoupled from the size of the signal wavelength. As a result, the sensors can sense signals over a wide range of frequencies, from the direct current (DC) to the Gigahertz (GHz) range, and theoretically up to the THz range.
SQUID arrays are now being explored for a wide variety of applications, including medical applications (such as low-field magnetic resonance imaging (MRI) applications, for example), geophysical exploration (e.g., oil and mineral location), non-destruction testing and RF detection purposes. With respect to RF detection, a SQUID-based RF detection device (antenna) would not work in a traditional sense (i.e., as traditional antennas do with resonance). Instead, and as mentioned above, SQUID arrays could detect minute magnetic fields, yet could be decoupled from the size of the wavelength corresponding to the generated magnetic field being detected. This means the SQUID antenna device could sense signals in the MHz range, but because of the decoupling aspect, the device could still be fully contained on a 1 cm×1 cm chip.
An important feature in signal detection is direction finding (DF). In order to develop a device able to sense a signal and determine the direction of propagation, a solid three-dimensional structure with a 2D chip that includes a SQUID on each side could allow simultaneous detection of all three components (Bx,By,Bz) of a magnetic field.
In view of the above, it can be an object of the present invention to provide a 3D SQUID array which can be small enough to be integrated onto a 1 cm×1 cm or similarly sized chip. Another object of the present invention can be to provide a 3D SQUID array having pyramidal geometry, but without sacrificing linearity of anti-peak response. Yet another object of the present invention can be to provide an antenna that incorporates SQUIDs to detect signals without resonating. Still another object of the present invention can be to provide a 3D SQUID array which can detect magnetic fields in three (orthogonal) dimensions. Another object of the present invention to provide a 3D SQUID array and method for manufacture that can be consistently fabricated in a cost-effective manner.